1. Field of the Invention
The present invention aims to provide new combustion equipment for a water tube boiler with a tube nested combustion chamber, and a new combustion method to use the equipment, whereby NOx levels are controlled by burning fuel in the water tube nest under high intensity combustion and reduction of the boiler size and weight is attained by making the furnace extremely small. The invention is applicable to all types of boilers, such as Natural Circulation, Forced Circulation, and Once-Through Water tube boilers and Flue & Water tube boilers such as Vacuum Hot Water Boilers, Re-generators of Absorption type Refrigerators, Domestic Hot Water Heaters and Steam Generators, and Heat Exchangers (hereinafter, these are referred to as Boilers).
2. Description of the Prior Art
In conventional types of boilers, a furnace occupies most of the volume of the boiler, thereby undesirably affecting the performance and the cost of the boiler. Therefore, it is desirable to develop a small but highly efficient boiler.
The inventors have proposed and developed the following two methods to reduce the volume of the boiler occupied by a furnace to nearly zero. One of the methods is a so called "High Intensity Surface Combustion Method" which attains high intensity surface combustion by use of a pre-mixed burner 12', (Japanese Patent Application No. S60-205104, refer to present drawing FIGS. 11 & 12). The second of the methods is a so called "Tube Nested Combustion Chamber Method" in which the combustion and heat transfer are attained by causing the flame 11' from the burner 12' to penetrate into the nest of tubes 1' (Japanese Patent No H2-272207, present drawing FIGS. 13 & 14).